This invention relates to detergent cleaning compositions which are particularly suitable for use in automatic dishwashers. In detail, the compositions herein comprise an alkoxylated nonionic surface-active agent, an aromatic sulfonated compatibilizing agent, a mixture of an alkali sulfate and an alkali sulfite, and are free of chlorine-containing bleach components. Both the nonionic surface-active agent and the compatibilizing agent are present in major amounts, preferably in about equiponderal quantities. The mixture of alkali sulfite and alkali sulfate is used in a major amount in a well-defined and narrow weight ratio. The compositions herein provide, during conventional use, markedly enhanced anti-redeposition benefits, particularly for soils composed of grease and grease-protein complexes. The instant compositions are also capable of providing improved cleaning benefits especially for burned-on soils. In addition to the essential components listed, the subject compositions preferably comprise conventional dishwashing composition additives in the art-established levels for their known functions. Examples of the like additives include sodium silicate solids, sodium carbonate, sodium bicarbonate and sodium phosphate.
Conventional automatic dishwashing compositions normally contain a low-foaming surface-active agent, a chlorine bleach, alkaline builder materials, and usual minor ingredients and additives. The incorporation of chlorine bleaches requires special processing and storage precautions to protect components which are subject to deterioration upon direct contact with active chlorine. In addition, the stability of the chlorine bleach itself is critical and raises additional processing and storage difficulties. It is also known that the chlorine-containing bleaches which are normally used in automatic dishwashing detergent compositions can tarnish silverware and damage the metal trim on china. Accordingly, there is a standing desire to formulate automatic dishwashing detergent compositions which are free of active chlorine and which are capable of providing overall hard surface cleaning and appearance benefits comparable to or better than active chlorine-containing detergent compositions. This reformulation is particularly delicate considering that during automatic dishwashing operations, active chlorine prevents the formation and/or deposition of troublesome proteins and protein-grease complexes on the hard surfaces and no surfactant is currently known capable of performing that function in the absence of chlorine bleach.
The majority of detergent compositions presently available contain inert filler salts such as sodium sulfate in varying levels up to, for example, 80%. U.S. Pat. No. 2,387,572 to Flett discloses that the detergent activity of alkylaryl sulfonates containing from 12 to 16 carbon atoms can be enhanced by the addition thereto of substantial amounts of a water-soluble salt having an inorganic cation selected from the group consisting of water-soluble sulfates, sulfites, thiosulfates, chlorides, dihydrogen phosphates, borates and acetates. U.S. Pat. No. 3,741,901 to Ziffer discloses detergent compositions containing surface-active agents and chelating agents, if desired, in combination with additional detergent composition additives and a water-soluble sulfite or bisulfite.
The disclosures of U.S. Pat. No. 3,549,539 to Mallows relate to machine dishwashing powders containing a nonylphenol-5-EO or a condensation product of a random C.sub.11 to C.sub.15 secondary alcohol and ethylene oxide with an HLB (hydrophilic-lipophilic balance) value between 11.5 and 13.5 and a polyethylene oxide-polypropyleneoxide condensate that consists of between 5 and 25% polyethyleneoxide and 95 to 75% polypropyleneoxide and has a molecular weight between 1500 and 2700. It is disclosed that, in addition to the above surfactant combination, the machine dishwashing powder will normally contain from 5 to 30% of a silicate such as sodium metasilicate, from 5 to 30% of an oxidizing agent, from 25 to 70% of a calcium-ion sequestrant and from 1 to 20% of an inorganic filler salt, such as sodium carbonate or sodium sulfate. The oxidizing agents can be represented by chlorinated sodium orthophosphate, chlorinated isocyanurate and perborate possibly with a copper catalyst or an organic activator. Additional disclosures relative to bleachcontaining detergent compositions for use in automatic dishwashers can be found in, for example, U.S. Pat. Nos. 3,410,804; 3,390,092; 3,248,330 and 3,595,968.
Various attempts have also been made to formulate bleach-free low-foaming detergent compositions for automatic dishwashing machines containing particular low-foaming nonionics, builders and filler materials and additives adapted to provide a particular function. For example, U.S. Pat. No. 3,022,250 to Grifo relates to low sudsing detergent compositions especially adapted for use in automatic dishwashing machines containing a phenol having therein an aliphatic substituent with an average of nine carbon atoms per chain and a second substituent comprising condensed ethylene oxide in an average number of four molecules per molecule of phenol together with builders consisting essentially of a mixture of sodium metasilicate and sodium tripolyphosphate in the proportion of 1 part of metasilicate to 3 parts of tripolyphosphate, the builders being present in the proportion of 95 parts of builder mixture to 5 parts of alkyl phenol ethylene oxide. The disclosures of U.S. Pat. No. 3,048,548 to Martin et al. relate to substantially identical subject matter wherein the nonionic low-foaming surface-active agent can be represented by very specific polyoxyalkylene glycol mixtures. U.S. Pat. No. 3,382,178 to Lissant et al. also pertains to automatic dishwashing compositions comprising a de-foaming nonionic surfactant having a specific formula and a small amount of an anti-oxidant for the purpose of reducing, inhibiting and/or preventing alkali degradation of the nonionic surfactant thereby rendering it stable in alkaline detergents, particularly during prolonged storage.
Concurrently filed U.S. patent application Ser. No. 479,953; entitled: AUTOMATIC DISHWASHING DETERGENT COMPOSITION; Inventors: Edward J. Maguire, Jr. and Robert A. Staab; relates to bleach-free detergent compositions for use in automatic dishwashers comprising an alkoxylated nonionic surface-active agent and a sulfonated aromatic compatibilizing agent, such as, for example, xylene-, toluene-, cumene- and benzenesulfonate.
Concurrently filed U.S. patent application Ser. No. 479,952; entitled: ENZYME-CONTAINING AUTOMATIC DISHWASHING DETERGENT COMPOSITION; Inventors: Geoffrey Place and Edward J. Maguire, Jr., relates to bleach-free automatic dish-washing compositions comprising an alkoxylated nonionic surface-active agent, a sulfonated aromatic compatibilizing agent such as, for example, xylene-, toluene-, cumene- and benzenesulfonate, and an enzyme having an iso-electric point greater than 8.5.
While the prior art clearly recognizes the disadvantages of using aggressive chlorine bleaches in automatic dishwashing operations and also suggests bleach-free compositions by merely leaving out the bleach component, said art does not disclose or suggest combinations of alkoxylated nonionic surfactants and particular compatibilizing agents in combination with well-defined sulfate-sulfite mixtures, leave alone predicting the performance advantages attainable when using the instant compositions in automatic dishwashing operations.
It is an object of this invention to provide bleach-free detergent compositions which can be used in automatic dishwashing operations.
It is an additional object of this invention to provide an automatic dishwashing detergent composition which exhibits improved anti-redeposition characteristics for soils composed of grease and grease-protein complexes, and superior cleaning performance, particularly for burned-on soils.
The above and other objects can now be met by formulating bleach-free detergent compositions comprising a specific active system and a combination of an alkali sulfite and an alkali sulfate.